An inspection of these assets completed towards the end of winter 2022 identified an area of land subsidence near one of the large lattice towers that supports these lines. The tower is in very steep terrain, and given the very wet winter, the Northpower team was concerned that subsidence may indicate that the ground in the area was unstable and that the tower may be at risk.
Specialist inspection and monitoring of the subsidence by Northpower’s geotechnical consultants confirmed that subsidence was indeed an indicator of a longer-term issue. Their work concluded that the foundations of the tower were likely to be undermined at some point, and if this was to occur, extensive damage to the line and extended power outages for the region could result.
On receiving this advice, our construction teams have been working tirelessly to engineer a solution that would remove dependency on the impacted tower. The first stage of these works involves the construction of two temporary bypass lines around the impacted tower, stage two will involve reengineering of the existing line to avoid the impacted area.
Before Christmas, the construction of the first of these bypass lines was completed. This has been a major undertaking due to the scale of the lines involved, the very steep terrain, and the ongoing wet weather during the construction of the line. Power is now flowing through that new line, and the impacted tower has been removed from service.
Removing the impacted tower from service eliminates the risk of widespread and extended power outages for the region, however, more work is needed to restore full security to the region. A fault on the new line would still result in a power outage, while repairs were made – in a worst-case scenario we could still see power out for around 8,000 customers for several days. Completion of the second bypass will reduce that time to a few minutes, and completion is scheduled for the end of March.
Given the continuing outlook of poor weather over the summer, Northpower wants our community to be aware that there is an elevated risk of outages during this time while we rely on a single line. This is a good reminder for people to be prepared and think about their contingency plans should something unexpected happen.
“It is a good idea to always be prepared for an unexpected power outage.
Keeping a full gas bottle for the BBQ, alternative forms of lighting in a handy place with batteries and your devices charged are practical steps we can all take”, COO of Northpower Network, Josie Boyd says.
The Civil Defence Get Ready website has some more helpful tips on how to prepare.
Northpower would like to thank Te Parawhau, Whangarei District Council, Northland Civil Defence, and our customers impacted by the work for their continued support as we work to resolve this risk.
We will update the community when the second line has been constructed and if there are any concerns people are welcome to contact our customer centre at 0800 667 847.